Geology Reference
In-Depth Information
Table 13.3: The worldwide depletion of the exergy reservoir of the main mineral
commodities. - continued from previous page.
B
,
ktoe/yr
(1900-
2008)
B
,
ktoe/yr
(1996-
2008)
B
,
ktoe
(1900-
2008)
Substance
reported
by USGS
Mineral
ore
P,
tonnes
(1900-
2008)
% R
loss
R/P,
yrs
Vanadium
V in other
ores
1.39E+06 3.61E+04 3.31E+02 1.22E+03 9.7
232
Wolfram
Scheelite
2.75E+06 5.02E+05 4.61E+03 8.76E+03 49.6
50
Zinc
Sphalerite
4.07E+08 2.34E+05 2.27E+03 5.58E+03 65.8
17
Zirconium
Zircon
3.31E+07 2.65E+05 2.43E+03 7.76E+03 28.4
65
Sum
8.48E+10 1.01E+08 9.28E+05 2.54E+06 35.8
142
Fig. 13.31 shows the cumulative production of the minerals evaluated, clearly
demonstrating the exponential increase suffered by most minerals in the analysed
period. Of all commodities, iron, the building block of industrialisation, has been
historically the most extracted metal, accounting for 67% of the total non-fuel
mineral extraction since the beginning of the 20th century. Phosphate rock follows
with its 8% relating to its extensive use in fertilisers for agricultural production.
Limestone and gypsum, which are significant building materials account for 7% and
6%, respectively. Aluminium (6%) is another metal that has played an important
role in industrialisation, especially since the second half of the last century.
Fig. 13.32 shows the contribution of the remaining commodities. These are
potash, from which potassium is derived (the third major plant and crop nutrient
after nitrogen and phosphorous) at 1.5% followed by copper (0.6%), a key metal
in the electric and electronic industry; the alloying metals manganese (0.6%) and
magnesium (0.45%) and zinc (0.48%), which is also an alloy and used in galvanising.
The natural bonus lost (exergy replacement costs) associated with the extrac-
tion of the main mineral commodities are represented in Fig. 13.33. Three of these
minerals: potash (38%), aluminium (27%) and iron ore (25%) account for major
degradation costs. This is because the exergy replacement costs include the irre-
versibility factor of technology through the unit exergy replacement costs, k. As
seen in Table 12.2, potash and aluminium have high k-values: 1,926 and 2,088,
respectively, while the k value of iron ore is only 164. In general, very abundant
minerals in the crust, with elevated crepuscular concentration values x
c
possess low
unit exergy replacement costs. These values are also influenced by the state of
technology. Indeed the more energy intensive a regular process of beneficiation, the
greater it is. Hence, in addition to tonnage, the exergy replacement costs take into
account the scarcity factor as well as the state of technology. So for instance, in the
case of potash, there are three factors which contribute to its ranking as one of the
most extracted: its greater concentration exergy, compared to that of aluminium
or iron (30.7 vs 16.6 and 17.7 kJ/mol, respectively); its high unit exergy cost value;
and the not insignificant quantities of mineral mined throughout the last century.
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